Alternating-current motor.



V. A. FYNN ALTBRNATING CURRENT MOTOR.

APPLICATION FILED JAN. 26, 1914.

Patented Dec. 29, 1914.

. I/VVE/VTOH Valera A. Fynn,

( I a I I ATTORNEY (7 WASHINGFON D, C

TATES P EN OFFICE- vi ssm. rYiviv, one. Louis, iviIssoUnI, .assienon TQWAGNER ELEGQTRIGTMANU- rAoTUnIive COMPANY, on ST. LOUIS, MISSOURI, ACORPORATION or MISSOURI.

ToaZZ whom it may concern:

Be itknow-n that I,1VA-Limn ALFRED FYNN, a subject of the King ofEngland, residing at St. Louis, Missouri, United States of America, haveinvented a certain new and useful Alternating-CurrentMotor, of which thefollowing is'such a full, clear, and exact description as will enableany one skilled in the art to whichv it appertains to make and use thesame, reference being had to the accompanying drawings, forming part ofthis specificationa My invention relates to' improvements in the classof induction motors in which the a motor of this class in which the useof moving contacts and normally idle wind-' dings or resistances on the,rotor" may be avoided,,thus more fully'utilizing the winding space onthe rotor under running conditions, and toavoid the use of a" startingtransformer and of allcomplicated switching operatioiis form-organizingthe stator connections after the motor has been brought up to speed.

winding and a low resistanceP pole winding which is permanently:short-'circuited so as to respond to a P pole magnetization. The

high resistance squirrelcage will, of course, respond to a magnetizationof any number of poles. The stator carries a main-Ppole -winding and anN pole starting winding. 1 These two stator windings are "connectedsnares at starting and, after the'motor has reached a sufficient speed,the .N pole winding is short-circuited. It will be understood that eachstator [winding may have any desired number of poles, the designations Pand N'being used to indicate that the stator windings produce difl'erentnumbers of poles. a

In the accompanying drawings, Figure 1 r is a diagrammaticrepresentation of a polyphase motor embodying my invention, and Fig. 2is an explanatorydiagram.

In Fig. 1, the stator 2 is provided with a number of holes-orslots 8, inwhich the stator windings are located. The rotor? carries a number ofslots 5 adapted to receive the rotor windings: Thefigure shows atwo-phase" IIIgS.

than through ALrEnNATinG-oUnn-Em Moron.

Specification of Letters Patent. Patentd Dc. 29, 1914. I Applicationfiled January 26, 1914. Serial No. 814,310.

motor, the stator of which is provided with 8 pole winding is the mainstator winding. The 4 pole winding isthe auxiliary, or starting, statorwinding. The lead 17 of phase ,A is connected to one end of the 4 polestator winding 9; the other s end of this winding is permanentlyconnected to one adapted 'to short-circuit the 4 pole. winding '9.Lead19. of phase B is connected to'one end of the 8 pole stator winding12;the

other endxof this winding-is permanently connected to one end of the 4pole stator winding '11, the other end of 11 being permanently.connected to lead 20 of phase B. The switch la-is adapted toshort-circuit thee: pole winding 11. The rotor carries a high resistancesquirrel cage, comprising a number of bars 6 connected at each end by ashort-circuiting ring 7.. A number of short-circuited coils'a areaalsodisposed in the rotor slots and span approximately oneeighth of therotor circumference, so as to beinductively responsive to the 8 polestator windings. v

The operation of this machine. is somewhat as. follows: Assuming, forexample,

that the, statonwindings are connected to a two-phase supply, as shownin Fig. 1, and that the short-circuiting switches 13 and 1d are 'open,thenthe voltage of each phase 'will distribute itself between the L polestarting and the 8 pole working windings of eachphase. The 8 polewindings of the two phases produce a rotary 8pole-field, which inducescurrents in-bothrotor wind- The auxiliary 4c pole. windings oiE the twophases produce'arotaryt pole field, which induces currents in therotorsquirrel cage only. -The'resistance of the squirrel cage'is chosenhigher than-that of the 8 a two-phase 8 pole and 4t pole-winding. The vpole rotor winding, the resistance of which is made very low. If themain andauxiliary stator windings have thesame number of ,turns, then,with the rotor at rest, it-will require a very much greater voltageto.force a given' current through the auxiliary the main stator winding..If, having the same number of turns,

these two windings are connected in series across a given voltage,thusbeing' forced to carry the same current, then almost all of theavailable voltage will be expended in driving the current through theauxiliary winding. The difference of potential across 5 this auxiliarywinding will be large, that across the main winding very small, with theresult that a very strong -l pole and an ex tremely weak 8 pole fluxwill he produced. I prefer to wind the auxiliary with fewer turns thanthe main winding and thus rei'ducenthis excessive diiierence between thetwo fluxes while still keeping the 1- pole v'greaterthan the 8pole fluxat starting. The

small 8 pole flux will, nevertheless, induce a .largecurrent in, the lowresistance 8 pole rotor winding. 7 Because of thelarge time ,constantofthis rotor winding, the current small '8gpoleflux will, induce but asmall currentingthe higlrresistance squirrel cage and,

although thiscurrent will be nearly in phase withthednducingfiux becauseof .thesmall' time constant of this rotor winding, yet the ':resultingtorque'will be small because of the "small. current. :The larger at poleflux will induce a largeand nearly cophasal current in the squirrelcage, thus producing a pow- 'erful starting torque. As thespeed of thez.

.IDZLCllI-IIB increases, the conditions w1ll change 1 somewhat, as shownin Fig; 2. The at pole torque .21 F\Vil1 diminish with increasing speedwhile the 8 pole torque 22 will raptidlyincrease with increasingspeeduntil a nearly synchronous 8 pole speed is reached,

.whenzthat torque. will decrease extremely chronous speed is, ofcourse,- twiceas great rapidly. and become zero at the moment.

"when the 8 pole synchronous speed is actually reached (point 15 of Fig.2). At that instant, the a pole torque still has an appreciable valueforit does not become zero until the 1 pole synchronous speed, point 16 ofFig. 2, vis reached. This 4 pole synas the 8 pole synchronous speed,butit can :never be reached by a well-designed motor I 53 1;;- ojthigpate nt may be obtained, for

fiof this kind, because, as soon as the 8 pole synchronous speed isexceeded, the 8 pole rotor-winding acts as a powerful brake, developinga negative torque, as approximately-indicated in Fig. 2 by that part ofthe torque line which is shown below the horizontal axis. This negative8 pole torque will prevent the motor shown in Fig. 1 from'materiallyexceeding the 8 pole synchronous speed. The resultant torque 13 of saidmotor will, at every instant, be the arithmetical sum of the 4 pole and8 pole torques. After-the rotor has reached a suiiicient speed, theswitches'13 and 14 should be closed, either by hand or automatically,thus short-circuiting the auxiliary stator wind ings 9,511, when themotorwill continue-to operate as an ordinary 8 pole machine.

These a pole windings may be safely shortcircuited, because theyare notinductively responsive to the mainS pole windings. The rotor windingswill be fully utilized in normal operation, because the main rotorwinding is an 8 pole winding and the auxiliary rotor winding is asquirrel cage which, of course, is responsive to an 8 pole induction.The auxiliary stator winding will be idle in normal operation unlessmeans are provided for reconnecting same so as to produce an 8 polemagnetization. Such-means would,

however, form Y an unwelcome complication and are best dispensed with.

The starting stator windings may be designedto produce a. greaterrnumberof poles than'the mainstator windings, and it is not necessary for: oneotthese windingsto have double the number of poles of the: other. It issufiicient that theatwo numbers of poles be so chosen as to avoideffective induction -between the two sets of windings.

, Havingw fully described my invention, what I claim as. new and d6S11GtO secureby Letters-Patent of the UnitediStatesis 1. In an inductionmotor, an inducing member provlded. with al? pole wlndmg and an N polewinding, said windings being connected in series, an induced member'pro--v1ded with a high resistance. squirrelucage winding and azlowresistance short-circuited P vpole winding, and means for. short-cir- 1cuiting the N- pole inducing winding.

2'. In an induction nrotor, an inducing member provided with a P polewinding and an N pole winding, an'induced member provided with a highwresistancez squirrel cage winding-and alow'resistance short-circuited'P pole winding, andmeans for shortcircuiting the N pole inducingwinding.

In an induction motor, an inducing member provided: with a P: polewinding and an N pole winding, said windings being connected in series,and an inducedmember provided=-. with a 'highresistance, squirrel cagewindingand a low resistance shortcircuited P pole'winding.

4'. In anunduction motor, an inducing member provided witlrmeans forproducing simultaneously an N-pole and a P pole magnetization, aninduced member affording a low resistance path for currents induced byone set of poles'of the inducing member and a high resistance pathforcurrents induced by both sets of poles of thezinducingmem- I her.

In testimony whereof, I have hereunto set a my h and and alii xed.myseal.

five, cents each, by; addressing. the f: Qnmmissioner. of Patents;

Washington, I). C.

